/**
 * @param {number} n
 * @return {number}
 */
 var countGoodNumbers = function(n) {
    const mod = BigInt(1e9+7)
    let odd = BigInt(n)>>1n, even = BigInt(n)-odd
    const quickMulti = (a,b) => {
        let ans = 1n
        while(b) {
            if(b&1n){
                ans = ans*a %mod
            }
            a = a*a%mod
            b >>= 1n
        }
        return ans
    }
    return quickMulti(4n, odd) * quickMulti(5n, even) %mod
};